K02 Tire Pressure? (1 Viewer)

[1MAC]

I put the LT285/65/18 E-rated KO2 tires on my 2015 LC about a month ago. Reading some of gaijin's posts about inflation tables, I went to the Toyo website and interpolated a value of 41 PSI. The Discount Tire salesman explained that their computer automatically figures out the correct pressure from the same tables and specified 40 PSI for my setup. Of course, they then inflated my tires to 36 PSI!

I feel like the correct pressure is obviously 41 or 42 PSI, but having checked tires many times with multiple gauges I know most of them are not accurate enough to really be sure what the true pressure is to within a pound.

My question is this: What is everybody airing these tires down to on the trail? We've always just aired our tires down to the 12-15 PSI range and never really gave it any thought.

 

[NCFJ]

I chalk my tires when new and then again at about 15K miles and set my pressure from there. There are many factors involved in finding the correct pressure, weight is a huge factor in the equation.

 

[gaijin]

I put the LT285/65/18 E-rated KO2 tires on my 2015 LC about a month ago. Reading some of gaijin's posts about inflation tables, I went to the Toyo website and interpolated a value of 41 PSI. The Discount Tire salesman explained that their computer automatically figures out the correct pressure from the same tables and specified 40 PSI for my setup. Of course, they then inflated my tires to 36 PSI!

I feel like the correct pressure is obviously 41 or 42 PSI, but having checked tires many times with multiple gauges I know most of them are not accurate enough to really be sure what the true pressure is to within a pound.

My question is this: What is everybody airing these tires down to on the trail? We've always just aired our tires down to the 12-15 PSI range and never really gave it any thought.

When I do the calc based on the Load/Pressure tables, I always round up so I get 42psi F/R for your application.

Tire shops, and tire manufacturers, when asked for a recommended pressure tend to recommend only the published pressures which are in increments of 5psi for this tire. This means they will determine either 40psi or 45psi depending on whether they round up or not. It's in the ballpark, but not very accurate.

I use one of these to measure tire pressure:

You can find it here: 99.99 PSI DIGITAL AIR PRESSURE GAUGE - Intercomp Racing

It's accurate to 0,1%, temperature compensated and barometric pressure compensated. It's obviously great at home in the shop, but can also be used to calibrate other gauges that you could use in the field.

Of course, ambient temperature plays a big role in how one sets the Cold Tire Inflation Pressure. Also, what does one do when adjusting pressures in a garage when the garage temp is different from the outside ambient temp? Toyota published a TSB that has a great table for determining the pressure to use when dealing with changing temps: https://attachments.priuschat.com/attachment-files/2015/10/96267_T-SB-0345-08.pdf Check out pages 3 and 4 for the Tire Pressure Adjustment chart and how to use it.

Now to your question: As far as airing down, you are correct, it is very situation dependent and it sounds like you are already aware of the dangers of airing down too far. All I can offer is a very general rule of thumb that will most likely not get you into any trouble: air down to 50% of the recommended Cold Tire Inflation Pressure. For example, in your case that would mean that you would air down from 42psi F/R to 21psi F/R as a starting point. If that still doesn't get the job done, then you could carefully air down further, but that would be very situation dependent.

HTH

 

[1MAC]

The mere fact that I was able to come up with the same result as gaijin when I researched the proper inflation pressure for my tires makes me very proud!
Thanks for the airing down advice, and that TSB. I've always wondered about the differences in temperature and its effect on inflation pressures.

 

[Utah200]

Been going by 1 PSI for every 10 degree ambient temp change for decades. PDF seems to roughly agree but makes it far more complicated.

Don't get too obsessed with this s***. A pound or two either direction ism't gonna make a hill of beans difference. You're chasing moving targets beyond the scope of the margin of error for everyone's tire gauge except gaijin's $300 kit.

50% starting point for air down? What would then determine max speed? Seems a bit low if you're just trying to smooth out washboards and cobbles that you can probably still run at 50 mph.

 

[gaijin]

Been going by 1 PSI for every 10 degree ambient temp change for decades. PDF seems to roughly agree but makes it far more complicated.

Don't get too obsessed with this s***. A pound or two either direction ism't gonna make a hill of beans difference. You're chasing moving targets beyond the scope of the margin of error for everyone's tire gauge except gaijin's $300 kit.

50% starting point for air down? What would then determine max speed? Seems a bit low if you're just trying to smooth out washboards and cobbles that you can probably still run at 50 mph.

If you're running at 50 mph, you should not be aired down at all.

 

[Utah200]

If you're running at 50 mph, you should not be aired down at all.

Perhaps, but that caveat is often overlooked when suggesting intermediary pressures for various surfaces. Point being that there's an endless set of variables and thus permutations for what to run and when. For any given pressure choice off tarmac there are new parameters within one ought to operate correct? How does one go about deciphering what the max speeds are for various surfaces / pressures?

 

[gaijin]

Perhaps, but that caveat is often overlooked when suggesting intermediary pressures for various surfaces. Point being that there's an endless set of variables and thus permutations for what to run and when. For any given pressure choice off tarmac there are new parameters within one ought to operate correct? How does one go about deciphering what the max speeds are for various surfaces / pressures?

Perhaps you're overanalyzing and perhaps I'm oversimplifying, but I really don't think airing down should be very complicated.

I would not air down to 50% for any situation that has me driving over about 20 mph.

 

[KLF]

So I just read this entire thread, I never really thought a group would have such a debate over a couple of psi

Anyhoo. I am running LT285/65R18 KO2s (E rated). These were installed by the dealer when I bought the truck 6 weeks ago. They were all at 34-35 psi according to the TPMS output on the dash, so I thought I was good, since the door jamb sticker said 33 psi.

Took them up to 42 psi this morning (all 5), will give it a try. Do I need to reset the TPMS?

While i was doing this, I kept track of which tire was going up on the TPMS outputs on the dash, so now I know which one is which on the list. Kinda dumb that the system can't figure this out.

 

[gaijin]

Anyhoo. I am running LT285/65R18 KO2s (E rated). These were installed by the dealer when I bought the truck 6 weeks ago. They were all at 34-35 psi according to the TPMS output on the dash, so I thought I was good, since the door jamb sticker said 33 psi.

Took them up to 42 psi this morning (all 5), will give it a try. Do I need to reset the TPMS?

Yes, you need to reset the TPMS:

HTH

 

[Dan Higgins]

I have been running the same setup (285/65 R18 E-rated KO2s) for about 8 months now. Once I corrected my bad reading of gaijin's advice (I thought he said 40) and set them to 42 they have been great. (They weren't bad at 40 - just not "gaijin approved"). I check them with a digital gauge about once a month. I did need to put more in over the winter (here in Denver) as the ambient temps in the morning were a LOT lower than had been the case a few weeks earlier. Not a big deal. My local DT who does free checks knows to set them at 43 (it is a 1 mile drive to their shop) so if I need a quick check first thing in the morning that is "close enough."

The TPMS on my MY16 tells the pressure for each time including the spare. That was a pain in the neck for a while as I would stress when 1 or 2 of the tires were 1 PSI different than the others. Then I realized how insane I was being and let it go.

 

[MrCWineMan]

The TPMS on my MY16 tells the pressure for each time including the spare. That was a pain in the neck for a while as I would stress when 1 or 2 of the tires were 1 PSI different than the others. Then I realized how insane I was being and let it go.

That's not insane, if the numbers aren't the same, your tires are at risk.....

Well maybe not, but my OCD is at risk.

Now, joking aside, are there specs on the accuracy of the TPMS sensors?

 

[kreiten]

I see what you did there ... pressure ...

@gaijin just wanted to double check to make sure I'm running my 285/70 R18 KM2's at the right pressure, what say ye sir? thanks in advance!

 

[Utah200]

@gaijin just wanted to double check to make sure I'm running my 285/70 R18 KM2's at the right pressure, what say ye sir? thanks in advance!

I think he said 20 PSI is perfect for Mondays, unless it rains.

 

[gaijin]

@gaijin just wanted to double check to make sure I'm running my 285/70 R18 KM2's at the right pressure, what say ye sir? thanks in advance!

Recomended Cold Tire Inflation Pressure for the LT285/70R18 KM2's on your LC200 is 38psi F/R.

HTH

 

[gaijin]

I think he said 20 PSI is perfect for Mondays, unless it rains.

You must not have been paying attention ... again.

Please don't misrepresent my posts.

Not sure who pi**ed in your Corn Flakes, but you can stop misdirecting your pettiness at me any time. It's getting old.

 

[Utah200]

Recomended Cold Tire Inflation Pressure for the LT285/70R18 KM2's on your LC200 is 38psi F/R.

HTH

You must not have been paying attention ... again.

Please don't misrepresent my posts.

Not sure who pi**ed in your Corn Flakes, but you can stop misdirecting your pettiness at me any time. It's getting old.

Lighten up Francis. Intewebs not so srs bzns

 

[belmontjoe]

Gaijin,

Could I trouble you for a pressure recommendation?

LC200
BFG KO2 35x12.50R17 load rating E

 

[Cruuzer]

I'm running the Yokohama GO15's in 275/70/18, one size up. They are not the E rated ones. What should I run on them? Currently dealer set them at 34

 

[NCFJ]

I've chalked my tires for years, always has worked for me

how to chalk tires - Google Search